The present invention is directed to a regulated length take-up device, and, more particularly, is directed to the appropriately structured, regulated length take-up device which is suitably applied to an instrument which feeds continually washing cloth by a regulated length for the purpose of blanket cylinder washing operation in a printing machine.
In offset printing, a blanket cylinder is usually washed in order to remove residual inks and paper powder each time a predetermined amount of printed sheets is outputted. When a washing apparatus wipes the blanket cylinder by means of washing cloth, the washing cloth fed by a washing cloth feeder roller travels past a pressure block and is taken up by a take-up roll. The take-up roll continually takes up the washing cloth by a regulated length.
In the prior art regulated length take-up device described above, consideration is given to taking up a regulated length of the cloth, aimed at its efficient use. Variations of the take-up diameter of the take-up roll make it impossible to achieve regulated length take-up. Various techniques have been devised to cope with this. For example, a technique disclosed by Japanese Unexamined Patent Application No. 1-314173 (disclosed in Dec. 19, 1989) has, on a take-up roll shaft, a lever which is urged by an air cylinder to carry out take-up operation. Disposed on the other side of the lever, i.e., opposed to the air cylinder, is a stopper integrated with a detector block which moves in response to variations of the take-up diameter of the take-up roll, in a manner that the stopper is capable of being in contact with the lever; the washing cloth is taken up until the lever driven by the air cylinder contacts the stopper. In the apparatus proposed by the disclosure, the contact face of the lever against the stopper has a curvature configuration which allows the stroke of the air cylinder to be controlled in a manner that a fixed take-up length is achieved at each position of the stopper which shifts in response to variations of the take-up diameter of the take-up roll. The disclosure claims that the regulated length take-up operation is achieved by varying the cylinder stroke in accordance with the change of the take-up roll diameter.
Such a prior art regulated length take-up device described as above fails to accurately measure the take-up roll diameter under slippage and friction which incur between the rod of the air cylinder and the take-up lever, and between a stopper pin and its pin receiver, when the air cylinder drives the lever. The air cylinder, the take-up lever driven by the air cylinder and the diameter detector block share the common line of action (a straight line), and this line is perpendicular to the longitudinal axis of the take-up roll. The overall width of the take-up device of this kind is usually, mainly determined by the layout of both the washing cloth feeder roll and the take-up roll; if the structure of the air cylinder extends substantially the width of the take-up roll, however, the width of the device must be wide enough to accommodate the required stroke of the cylinder.